1. Field of the Invention
The present invention relates to a liquid discharge head used for an ink jet recording head or the like, and a liquid discharge apparatus. The invention also relates to an IC package structure. Among them, the invention is particularly effective in the application to the so-called side shooter type liquid discharge head having substantially the perpendicular discharge direction of ink liquid droplets or the like to the assembling surface of the substrate thereof.
2. Related Background Art
In conjunction with FIG. 12, the description will be made of the conventional liquid discharge head, such as an ink jet recording head. The ink discharge area A of a head shown in FIG. 12 is formed in such a way that the ink supply port 111 is provided in a silicon substrate 110 by means of chemical etching or laser or some other light energy; the electrothermal converting element 112 that serves as a discharge energy generating member is arranged on the silicon substrate 110; the covering resin layer 120 that becomes the walls of an ink flow path 121 is provided; and the ink discharge port (orifice) 122 is formed in the covering resin layer 120. The method of manufacture thereof is publicly known by Japanese Patent Laid-Open Application No. 06-286149 and others.
For the aforesaid side shooter type ink jet recording head, the distance between the ink discharge port 122 and the electrothermal converting element 112, that is, an orifice distance, can be formed easily by means of a photolithographic technique. Accordingly, it is possible to manufacture an ink jet recording head that can consistently discharge small liquid droplets of ink.
The structural character of the side shooter type ink jet recording head has the following requirements:
1. The thickness thereof should be smaller in the bubble growing direction or the ink discharge direction. With a shorter distance between the covering resin layers, having the orifices formed therefor, and a recording sheet (paper), namely, the distance to the recording sheet (paper), it becomes possible to prevent the head and the recording sheet from rubbing against each other due to the deformation (cockling) of the recording sheet. The cockling results from the curling of paper by changes of environment or the swelling of fibers caused by the permeation of ink into paper. With the shorter distance between the covering resin layer and the recording sheet, it is also possible to make the deviations of target position of impact smaller so as to obtain a desired image. More specifically, the distance to a recording sheet (paper) is required to be approximately 1 mm.
2. The electrothermal converting elements should be formed in high density on the assembling surface of the substrate perpendicular to the ink discharge direction or the bubble growing direction. More specifically, it is required to provide them in a precision of 600 to 1,200 dpi or more than 1,200 dpi.
In order to attain these requirements efficiently, the head shown in FIG. 12 is provided with a driver built-in area 123 formed on the silicon substrate 110. The control circuit for the aforesaid electrothermal converting element 112 is incorporated here. The electrodes of a flexible printed substrate (FPC) 130 and the electrodes of the silicon substrate 110 are positioned to face each other on the assembling area B of the silicon substrate 110, which are connected through an anisotropic conductive film or the like (not shown). The connecting portion is sealed and protected by a sealing resin 131. In this manner, the assembling structure is adapted to connect with an external circuit (not shown).
In this case, the bubble growing direction, that is, the thickness of the ink jet recording head in the ink discharge direction, is determined by the height of assembling, that is, the thickness (approximately 25 to 150 xcexcm) of the flexible printed substrate 130, and the thickness of the sealing resin 131 provided for the connecting portion.
The bubble growing direction of this assembling structure, that is, the assembling surface in the direction perpendicular to the ink discharge direction, there is contained the aforesaid built-in control circuit for the electrothermal converting element 112 on the driver built-in area 123 on the silicon substrate 110 described above. The control circuit and the electrothermal converting element 112 are formed by means of photolithographic technique.
Consequently, even when the ink discharge port has a precision of 600 dpi or more, the assembling density can be made as roughly as 100 to 400 xcexcm on the assembling area B where the source supply of electric power for the control circuit and electrodes on the input control signal side are drawn by use of the flexible printed substrate.
Next, in conjunction with FIG. 13, the description will be made of another conventional example disclosed in the specification of Japanese Patent Laid-Open Application No. 06-286127. Here, it is devised to make the thickness of the head smaller by externally installing an IC component (driving element) 223 for control use with inclination to the side opposite to the discharge direction of droplet ID to a recording medium P from the orifice (ink discharge port) 222 formed on the covering resin layer 221 on the substrate 210. The assembling density of the assembling area B on the flexible printed substrate 230 is almost equal to the density of the orifice 222 and the electrothermal converting element (not shown), and the control IC component 223 is connected to the flexible printed substrate 230 by means of die-bonding wire, and then, covered by the sealing resin 231. Consequently, to be in high density is dependent on the assembling density of the flexible printed substrate 230. In this respect, a reference mark IT designates an ink tank.
Now, to meet the demand for enhancing the printing quality and printing speed, the side shooter type ink jet recording head is required to be elongated. However, when the driver built-in head as shown in FIG. 12 is elongated, the following problems are encountered with respect to the assembling structure.
1. A number of substrates that can be taken from one wafer are reduced, leading to the increase in manufacturing costs. For example, in a simulation of a 4-inch recording head with the structure that has the control circuit incorporated therein, the size of the 4-inch recording head becomes approximately 8 mmxc3x97100 mm. However, only four of them can be taken from a 5-inch wafer; nine from a 6-inch wafer; and twenty-one from an 8-inch wafer.
2. The non-defective ratio becomes smaller. Assuming that the general CMOS process crystalline defect ration D≃0.003, the yield of the built-in control circuit is worked out. Then, no perfect products are obtainable from a 5- or 6-inch wafer. Also, only one perfect product is obtainable from an 8-inch wafer eventually.
For reference, the non-defective ratio is expressed by Y=exp (xe2x88x92Sxc3x97D), S (area)=XY.
This brings about an extremely serious problem in the production when the head is elongated.
Also, for the conventional example of the ink jet recording head shown in FIG. 13, the assembling density on the assembling area of the flexible printed substrate 230 is substantially equal to the density of the orifice 222 and the electrothermal converting element provided for the ink discharge port area A.
However, since wiring is formed by copper foil or the like on the flexible printed substrate 230 which is formed by polyimide or the like, the limit of the precision degree is approximately 500 dpi, and there is a problem encountered that the elongation is possible only up to approximately 25 mm in terms of the practicable dimension in consideration of the stretch and contraction thereof caused by the linear expansion coefficient of polyimide and others.
It is one of the objects of the present invention to provide a liquid discharge head, a liquid discharge apparatus, and an IC package structure, for which promotion is possible to make the preciseness of the head higher still, and also, to the thickness thereof smaller and the length larger, as well as to make the printing speed significantly faster, while enhancing the production yield and increasing the number of substrates taken to contribute to reducing the costs of manufacture.
It is another object of the invention to provide a liquid discharge head which comprises an element substrate having on one surface thereof energy generating element for generating energy to be utilized for discharging liquid from a liquid discharge port, and a liquid supply port communicated with the liquid discharge port; a printed substrate provided with an external fetch electrode; and an IC component for control use for the energy generating element having provided therefor an output side electrode connected with the energy generating element and an input side electrode connected with the external fetch electrode. For this liquid discharge head, at least the aforesaid output side electrode of the IC component for control use is provided for the one surface of the element substrate.
It is still another object of the invention to provide a liquid discharge apparatus which comprises a liquid discharge head comprising an element substrate having on one surface thereof energy generating element for generating energy to be utilized for discharging liquid from a liquid discharge port, and a liquid supply port communicated with the liquid discharge port; a printed substrate provided with an external fetch electrode; and an IC component for control use for the energy generating element having provided therefor output side electrode connected with the energy generating element and input side electrode connected with the external fetch electrode, at least the aforesaid output side electrode of the IC component for control use being provided for the one surface of the element substrate, and conveying means for conveying a recording medium to face the liquid discharge port of the liquid discharge head.
It is a further object of the invention to provide an IC package structure provided with an IC component for control use and a flexible printed substrate. For this IC package structure, the flexible printed substrate comprises a first external fetch electrode directly connected with the extruded electrode of the IC component for control use individually, and a second external fetch electrode directly connected with the electrode of an assembling substrate for assembling the IC component for control use.
In accordance with the present invention, the IC component for control use is assembled face down on the substrate. Then, this is connected with the external power supply source and others by use the flexible printed substrate. Therefore, as compared with the case where the driver (driving element) for the discharge energy generating element is incorporated on the assembling substrate, the nondefective ratio of finished products can be enhanced. Also, the invention contributes significantly to the head elongation and the higher preciseness thereof.
Further, the present invention is arranged to enable the supply ports, for use of the liquid supply, to be open to the element substrate having at least the output side electrode of the IC component for control use provided therefor. This arrangement is favorable from the standpoint of thermal stabilization. Particularly, it is preferable, from the standpoint of structural arrangement, to arrange the liquid supply port and the printed substrate on opposite sides of the IC component for control use.
With the structure in which both the input side electrode and the output side electrode of the IC component for control use are installed on one surface of the integrated substrate, the positioning precision is made higher for the electrodes to enhance the reliability of the electrode connection. Further, it is easier for the integrated substrate, to which all the electrodes of the IC component for control use, to become thermally uniform. This is particularly preferable in terms of the reliability of electrode connection.
The extrude electrode of the IC component for control use on the input side is directly connected with the external fetch electrode of the flexible printed substrate, which enables the assembling substrate to be made smaller and a number of substrates taken to be increased. In this way, the productivity of the liquid discharge head is significantly enhanced to implement the manufacture of an elongated and highly precise ink jet recording head and others at lower costs.
Also, the second external fetch electrode provided for the flexible printed substrate is connected direction with the assembling surface, which enables the wiring resistance of the control circuit, which controls the discharge energy generating element on the assembling surface, to be reduced significantly to improve the driving efficiency of the discharge energy generating element, while enhancing the printing quality and printing speed as well. Further, this arrangement contributes to making the chip size of the IC component for control use smaller or the like.